A lot of workshops have experience with stability control systems and a lot of workshops have none, so Diesel Workshop has more FAQs on EBS, TEBS, RSC, ABS, and EBS. The fitment of such systems has been sporadic in the past. This situation is about to change with the mandatory fitting of some form of stability control making its way through to law. Now anyone dealing with truck and trailer maintenance has to be up to speed with just what the implications are of fitting these kinds of systems onto a vehicle.
Diesel Workshop would like to thank and acknowledge the Australian Trucking Association’s (ATA) Technical Industry Council whose Technical Advisory Procedure (TAP) is the reference on which this article was based. The aim is to provide trucking operators with key information about the fitment and operation of stability control systems for improved vehicle safety.
Here are a few Frequently Asked Questions:
QUESTION: What is CAN-bus?
ANSWER: CAN-bus is a system of communication between two or more electronic systems. Controller Area Network (CAN or CAN-bus) is a BUS standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer. The power train systems (engine, transmission and instrument panel) will typically have a system and the EBS system linking the braking elements is another.
Use of CAN communication enables far greater speed of signal to trailing units, and also the sharing of data between systems, allowing the truck master system to alter trailer braking as appropriate.
The key to this system is the CAN communication between vehicles and trailers in a combination. Through each vehicle providing information to the prime mover, deceleration can be matched between the prime mover and trailer. Brake timing is also improved. This means that the brakes come on together, and if the combination is loaded differently over each axle group, brake effort will be adjusted to give a far smoother deceleration, with no wheel lockup and no pull or push at the couplings. The best CAN performance is achieved with a 24V system.
QUESTION: What is the technical operation of RSC and load share functions?
ANSWER: For trailers equipped with TEBS, RSC logic control units can prevent roll-over within the vehicle’s physical limits. RSC is a function integrated in the software and hardware of the TEBS modulator. The system assesses vehicle data such as wheel speed, load information, and by means of an integrated sensor, lateral (transverse) acceleration data. By analysing this data, the TEBS unit detects the chances of roll-over and automatically applies the brakes.
No system can defy the laws of physics, and a trailer can still tip if the side forces are extreme or increase significantly during braking, but RSC significantly reduces this risk.
Operation is normally as follows: at a calculated point of lateral acceleration, the TEBS will apply a test pressure to the brakes. This is a very low, short duration pressure of which the driver is normally unaware. TEBS then monitors wheel speed reaction on both sides of the axle. If both wheels react together, the acceleration is allowed to increase, all the while applying test pressures, until the inside wheel speeds react differently from the outside, representing a loss of traction on the inside wheel. At this point, TEBS applies braking to slow the combination road speed.
QUESTION: Does TEBS have a weight scale function?
ANSWER: Yes. TEBS has an integrated load function, which can be accessed through an optional trailer monitor unit.
QUESTION: Do I require a blue or modification plate sign-off for retrofitting the roll stability function to the trailer?
ANSWER: Yes. An authorised vehicle examiner engineering (AVE) signatory needs to inspect the installation and approve as per regulatory requirements in your state or territory. This is because the brake system is being altered from original settings. Ask your engineer to include a clause regarding roll stability function on the sign-off form.